1. Field of the Invention
The present invention generally relates to a circuit device, and in particular, to a circuit device for driving a light source.
2. Description of Related Art
Liquid crystal displays (LCDs) have gradually become a mainstream display among others. LCD panels are actually electronic controlled light valves and produce visible images by the use of light driver circuit devices. LCDs generally use cold cathode fluorescent lamps (“lamps” for short hereinafter) to provide light sources. Other light driver circuits, such as light emitting diodes (LEDs), also attract some attention, but the applications of them are limited due to the high costs. Since the LCDs are consumer products, besides performances, an overriding factor in design is the cost. Therefore, one of the most important targets in design of the LCD light driver circuits is to reduce the cost.
FIG. 1 shows a conventional light driver circuit device and a lamp assembly. Referring to FIG. 1, an inverter circuit 14 is coupled to a plurality of lamps 11, 12, . . . , 13, for example. Generally speaking, the inverter circuit 14 may convert a DC power source 140 into an AC power source required by the lamps 11, 12, . . . , 13.
For the current applications of medium or small-sized light driver circuits, the liquid crystal screen of a notebook or a desktop computer requires one to four lamp assemblies, and thus the number of the inverter circuits must be one to four sets. Since a large-sized light driver circuit requires more lamps, the inverter circuit uses several sets of transformers 141, 142, . . . , 143 to drive the lamps 11, 12, . . . , 13 in a single side drive mode in FIG. 1. However, with the application of the light driver circuit, the size of the LCD is made to be larger. Therefore, in order to overcome the non-uniform luminance distribution of the light driver circuit device due to the leakage current, a double side drive mode has been provided in the prior art.
FIG. 2 shows a conventional light driver circuit device in the double side drive mode and a lamp assembly. Referring to FIG. 2, the light driver circuit device is installed with two sets of inverter circuits 14, 21, each having a plural sets of transformers 141, 142, . . . , 143 and 211, 212, . . . , 213 respectively coupled to both terminals of the lamps 11, 12, . . . , 13. Although the double side drive mode may reduce the leakage current, the number of the elements required by the inverter also increases, thus increasing the cost of a printed circuit board (PCB). If the number of the elements can be reduced, the cost will be relatively lowered, thereby achieving the current main purpose of the backlight design technique.